Apparatus for conducting sweetening operations



Nov. 15, 1955 s. ARTHURS 2,723,945

APPARATUS FOR CONDUCTING SWEETENING OPERATIONS Filed April 8, 1953HYDROCARBON CHARG E 56 24 :22 L fi- K20 26 F'IG.|. W CAUSTIC hREGENERATOR l 28 i E 48 64 6 TREATED H /4- 32 4 HYDROCARBON I I I 1 H 44WATER WATER J 52 I n- HEATER. 34. -c

TREATING CHEMICALS 4- FIG 2 EDUCTOR WASHING 1 SECTION COALESCING OXYGENSECT'ON CONTAINING 50 GAS COALESCING sacnom INVENTOR.

, I STANLEY ARTHURS *b HIS ATTORNEYS.

APPARATUS FOR CONDUCTING SWEETENING OPERATIONS Stanley Arthurs, Solon,Ohio, assignor to The Standard Oil Company, Cleveland, Ohio, acorporation of Ohio This invention relates to an apparatus forconducting sweetening operations on gasoline, naphthas, heating oils,kerosene, and the like.

The presence of elemental and combined sulphur in petroleum introducessepecial problems into the refining of the lower-boiling fractions, suchas the gasolines and kerosene. The sulphur in the higher-boilingpetroleum fractions, except for traces of hydrogen sulfide, is generalyin the form of stable and neutral organic compounds, which have nodeleterious effect on the oil; and generally no effort is made to removethem. The lower-boiling fractions, such as gasoline, occasionallycontain elemental sulphur in small proportions, which must be removed byspecial procedures. Hydrogen sulfide is nearly always present and isremoved by any simple method of washing the hydrocarbons with an aqueousalkaline reagent, such as caustic soda and the like.

Cracked naphthas nearly always contain small quantiusualy a portion ofthem is removed by caustic soda solution; the remainder is commonlytransformed by a special oxidation procedure, sweetening, into the lessodoriferous alkyl disulfides which remain dissolved in the oil.

Cupric chloride is now in extensive use to oxidize the mercaptans oflight oils to disulfides and thus sweeten the oils. The copper salt isreduced duringthe sweetening operation to the cuprous salt, but isre-oxidized by air at normal temperatures, the regeneration beingsimultaneous with the conversion of the mercaptans, if dry or solidcopper salt is used, or by a separateoperation if an aqueous solution ofthe copper salt is used. Some petroleum refiners use boththe solid andliquid processes.

Hydrogen sulfide is conventionally removed from sour naphtha by analkaline wash before copper sweetening, because copper sulfide whichwould form therefrom cannot be regenerated to an active sweetening agentby atmospheric oxidation.

In accordance with the present invention, a single unit of apparatus isprovided for conducting sweetening operations and more particularly,those operations known as copper sweetening.

Among the advantages resulting from the use of the apparatus of theinvention are savings in space requirements, reduced piping costs,reduced steel requirements for vessels and simplification of operation.

The invention will be further illustrated by reference to theaccompanying drawings in which:

Figure 1 is a sectional view in elevation of one embodiment of theapparatus of the invention;

Figure 2 is a sectional view taken on line 2-2 of Figure 1.

The drawings show a typical installation for treating 7,500 barrels perstream day of sour kerosene, but any other low-boiling hydrocarbon maybe treated in a similar manner.

2,723,945 Patented Nov. 15, 1 955 The apparatus as illustrated iscomposed of a vessel that is divided across its vertical length intothree compartments; a prewash compartment 20, a separatory cornpartrnent10 and a treating compartment 54. The separatory compartment 10 is inturn divided into three sections as illustrated in Figure 2; i. e., acoalescing section 12, a coalescing section 14 and a washing section 16.Each of the coalescing sections is packed with a coalescing material 15which is capable of removing water from hydrocarbons. The prewashcompartment is provided with an inlet pipe 24 and an outlet pipe 26, theoutlet pipe 26 being connected to pump 28 and to caustic regenerator 30and rejoining mixing valve 56. The interior of the prewash compartmentis provided with an outlet. pipe 22 having an opening near the top ofthe prewash compartment 20 which leads to coalescing section 14. Thecoalescing section 14 is provided with outlet pipes 40 and 32, thelatter of these pipes leading to heater 34, pump 36, eductor 8 andthence through pipe 38 into the treating compartment 54. Outlet pipe 40leads to waste. The bottom of the treating compartment 54 is conicallyshaped and is provided with outlet pipe 6 which is also connected toeductor 8. The discharge side of pump 36 is provided with a means 39 foradmitting cupric chloride and clay to the system. Connected to the inletside of pump 36 is pipe 62 which serves the purpose of admitting oxygenor an oxygen-containing gas such as air into the system.

The treating compartment 54 is also fitted with a dis charge pipe 42which leads to mixing valve 64 and to pipe 48 and thence to washingsection 16 of the settling compartment 10. Connected to the bottom ofthe washing section 16 is an outlet pipe 44 and a pump 46 the dischargeside of which is connected to line 42 just prior to the mixing valve 64.The washing section 16 is also provided with an opening or orifice 18leading into the upper part of coalescing section 12. Coalescing sction12 in turn is provided with two outlet pipes, an upper outlet pipe 50and a lower outlet pipe 52. r l

The operation of the apparatus is as follows:

The prewash compartment 20 is filled initially with aqueous causticsolution. The sour hydrocarbon, which may be kerosene or anotherlow-boiling fraction, is charged continuously to the system throughmixing valve 56 wherein it is mixed with recycled aqueous causticsolution and the resulting mixture is then injected via pipe 24 into theprewash compartment 20 for the purpose of washing the hydrocarbon andremoving any hydrogen sulfide which may be present in the feed. Thecaustic solution having a higher density than the hydrocarbon settles tothe bottom of the prewash compartment and is recirculated through pipe26 by pump 28 through caustic regenerator 30. From the causticregenerator the caustic solution is returned to mixing valve 56. Insteadof employing the regenerator, fresh caustic may be used, if desired, andthe spent caustic sent to waste.

The prewashed hydrocarbon rises to the top of the prewash compartmentand flows into an outlet pipe 22 and thence into the coalescing section14. (The coalescing sections are packed with glass wool or a similarmaterial 15 which is capable of removing aqueous components which may becarried into the coalescing section with the hydrocarbon.) The coalescedwater (or aqueous caustic) settles to the bottom of coalescing section14 and is i discharged from the system through pipe 40.

The prewashed hydrocarbon is withdrawn from coalescing section 14through pipe 32, passed through a heater 34 to insure complete solutionof small amounts of water which may be retained by the hydrocarbon, andis then pumped by means of pump 36 through the eductor 8 and pipe 38into the treating compartment 54. The treating chemicals, e. g., cupricchloride and clay, are

added as necessary to the discharge line of the pump 36 through pipe 39.

The treating chemicals that are present in treating 'compartmenti54'settle into the conically shaped bottom of the treating compartment andare removed through pipe 6 via eductor 8 and are then returned throughline 38 to the treating compartment 54. In this operation the treatingchemicals react with the mercaptan sulphur present in the hydrocarbonand thus sweeten the hydrocarbons. Continuously with this operation,oxygen or an oxygen-containing gas is admitted to the system throughline 62. The oxygen or oxygen-containing gas thus admitted is admixedwith the hydrocarbon and chemicals which enter the treating compartment54 and the treating agents are constantly regenerated by reaction withoxygen.

The sweetenedhydrocarbon is withdrawn continuously from the top of thetreating compartment through pipe 42, mixed with a stream of circulatingwater withdrawn from the washing section 16 by pump 46, and the mixtureof water and hydrocarbon is pumped through line 48 into the washingsection 16 wherein the last traces of treating chemicals are removedfrom the hydrocarbon.

Within the washing section 16 the water settles and is recirculatedthrough line 44 while the hydrocarbon rises to the top of the washingsection and flows through the opening or orifice 18 into the secondcoalescing section 12. Within the coalescing section 12, which is alsopacked with glass wool or a similar material 15, any water which iscarried over in the hydrocarbon from the washing section is removed fromthe hydrocarbon, settles to the bottom of coalescing section 12 and isdischarged therefrom through pipe 52. The treated kerosene, which is nowsubstantially free from mercaptan components, is withdrawn from thecoalescing section 12 through line 50 to storage.

From the above description it can be seen that the apparatus of thepresent invention is capable of performing a continuous processinvolving a multiplicity of steps. The use of the apparatus providesmeans for conducting sweetening operations in which much of theequipment formerly required to perform such operations may beeliminated.

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention withoutdepartingfrom the spirit thereof, and the invention is to be restrictedonly in accordance with the appended claims.

I claim:

1. An apparatus for treating hydrocarbons comprising a vessel dividedinto an upper compartment, a central compartment and a lowercompartment, said central compartment being divided into a firstcoalescing section, a second coalescing section and a washing section;means for feeding liquid into said upper compartment; an outlet pipehaving an opening near the top of and within said upper compartmentconnecting with said first coalescing section and means for transferringliquid from said first coalescing section successively through the lowercompartment, the washing section, the second coalescing section andthence to storage.

2. An apparatus according to claim 1 in which the means for transferringliquid from the first coalescing section to the lower compartmentincludes a heater.

3. An apparatus according to claim 1 in which said lower compartment hasa conically shaped bottom and the means for transferring liquid from thefirst coalescing section to the lower compartment includes means forsimultaneously withdrawing liquid and chemicals from the conicallyshaped bottom of said lower compartment.

4. An apparatus for treating hydrocarbons comprising a vessel dividedinto an upper compartment, a central compartment and a lowercompartment, said central compartment being divided into a firstcoalescing section, a second coalescing section and a washing sectionand said lower compartment having a conically shaped bottom; means forfeeding liquid into said upper compartment; means for withdrawing liquidfrom the bottom of said upper compartment; an outlet pipe having anopening near the top of and within said upper compartment connectingwith said first coalescing section; means for Withdrawing liquid fromnear the bottom of said first coalescing section; means for transferringliquid from said first coalescing section to said lower compartment;means for feeding an oxygen-containing gas and treating chemicals to theliquid being transferred by said last named means; means fortransferring liquid from an upper portion of said lower compartment tosaid washing section; an opening in the upper portion of said Washingsection leading into said second coalescing section; means forwithdrawing liquid from near the bottom of said second coalescingsection; and means for withdrawing liquid from the second coalescingsection at a point above the last named means.

5. An apparatus according to claim 4 in which the means for transferringliquidfrom the first coalescing section to the lower compartmentincludes means for simultaneously withdrawing liquid and chemicals fromthe conically shaped bottom of said compartment.

References Cited in the file of this patent UNITED STATES PATENTS1,652,399 Dickey Dec. 13, 1927 1,684,489 Halloran Sept. 18, 1928 r1,792,003 Dickey etal. Feb. 10, 1931 2,098,713 Wesselmann Nov. 9, 1937(I e w I

1. AN APPARATUS FOR TREATING HYDROCARBONS COMPRISING A VESSEL DIVIDEDINTO AN UPPER COMPARTMENT, A CENTRAL COMPARTMENT AND A LOWERCOMPARTMENT, SAID CENTRAL COMPARTMENT BEING DIVIDED INTO A FIRSTCOALESCING SECTION, A SECOND COALESCING SECTION AND A WASHING SECTION,MEANS FOR FEEDING LIQUID INTO SAID UPPER COMPARTMENT; AN OUTLET PIPEHAVING AN OPENING NEAR THE TOP OF AND WHEREIN SAID UPPER COMARTMENTCONNECTING WITH SAID FIRST COALESCING SECTION AND MEANS FOR TRANSFERRINGLIQUID FROM SAID FIRST